Variable condenser



H. H. SHOTWELL VARIABLE CONDENSER Fileq June 27, 1924 2 Sheets- Shee 1 Inventor. M/ /W Aug. 14, 1928.

1,680,810 H. H. SHOTWELL.

VARIABLE CONDENSER Filed June 27, 1924 Mimi 2 Sheets-Sh eet 2 Patented Aug. 14, 1928.

* UNITED STATES PATENT OFFICE.

HAROLD H. SEOTWELL, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE OPERADIO COB- PORA'IION, OF CHICAGO, ILLINOIS. A. CORPORATION OF ILLINOIS.

VARIABLE CONDENSER.

Application filed June 27, 1924. Serial No. 722,655.

The present invention has for its object to produce a simple and novel variable condenser having within the same means for securing a Vernier adjustment without the use 6 of aseparate Vernier plate, and without requiring that a knob be turned 1n opposite directions to secure first arough ad ustment and then a fine adjustment.

The various features of novelty whereby my invention is characterized will hereinafter he pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawings, wherein Figure 1 is an end or a front elevat1on of a device embodying the present invention; Fig. 2 is a section taken approximately on line 22 of Fig. 1, showing the device, to-

gether with a fragment of a panel on which the same is mounted; Fig. 3 is a section taken approximately on line 33 of Fig. 2; Fig. 4 is a section taken approximately on line 44 of Fig. 2; and Fig. 5 is a section taken approximately on line 55 of Fig. 1, only a fragment of the device being shown.

Referring to the drawings, 1 and 2 representtwo metal discs held in fixed spaced relation to each other by means of three parallel rods, 3, 4 and 5 placed at equal distances apart near the peripheral edges of the discs. The rod 3 is in metallic contact with the discs and forms one terminal. of the condenser. The rods 4 and 5 are insulated from the discs and one of them forms the other terminal of the condenser. The insulation between the rods 4 and 5 and the discs may take any usual or preferred form. As shown in Fig. 5, the rod 4 has thereon bushings 6 and 7, of insulating material, these bushings fitting into the enlarged openings in the discs through which the rod passes and having enlargements or flanges at their outer ends to engage with the outer facesof the discs and thus hold the head 8 a on one end of the rod and the nut 9 on the other end out of engagement with the discs. The rod 5 is mounted in a similar manner. The stationary plates 10 of the condenser are mounted on the rods 4 and 5, the plates be ng spaced apart by means of spacing washers 11 and being insulated from the discs 1 and 2 by means of insulating sleeves I shafts.

the same and at the centers thereof. The

shaft is supported at one end in an elongated hub 17 projecting outwardly from the disc 1 and extends through this hub and is provided on its outer end with a pointer 18. The opposite end of the hollow shaft termi nates a short distance from the rear disc 2 and has attached thereto a resilient spider 19 arranged-at right angles to the axis of the shaft. In the arrangement shown, this spider has three radial arms. Mounted on the freeend of each of the arms of the spider is a Wheel 20 in the shape ofa short frustum of a cone. The disc 2 is either recessed on its inner face or is made dishshaped, the depression or recess being pointed by an annular wall 21 co-axial with the tubular shaft and inclined to form a track on which the inclined faces of the wheels 20 may run. Extending, axially through the tubular shaft 16 is an actuating shaft 22 having on its outer end beyond the pointer 18, a knob 23 by means of which it may be turned. The inner end of the shaft22 extends somewhat beyond the corresponding end of the surrounding shaft, and is provided with a small cone-shaped wheel 24 occupying the reverse position with respect to the wheels 20 andengaged at its periphery with the inclined peripheral surfaces of the wheels 20. It will be seen that if, when the parts are assembled, the resilient spider. is placed under'an initial tension', it serves to force the wheels 20 against the inclined annular track. It will also be seen that if the actuating shaft 22 is pushed or drawn in that direction in which it would move by pull upon the knob, the wheel 24 disc 2, the set screw being co-axial with the j it engages with the end of the shaft 22, any

When the set screw is turned until further turning movement results in pressing the wheel 24 against the wheels 20, Where it will remain until wear takes place. Whenwear occurs, it may be compensated for by simply adjusting the set screw. Since the set screw is intended to remain stationary, while the shaft 22 is adapted to be rotated, a locknut 26 is placed on the set screw to prevent it from being accidently turned by the shaft. In the arrangement shown, a small ball 27 is placed between the inner end of the set screw and the end of the shaft 22, or rather the small wheel that forms the end of the shaft, thus reducing the friction.

When the knob is turned to adjust the condenser, the small wheel 24: acts on they wheels 20 to rotate the latter. Since the Wheels 20 are in engagement with the stationary annular track 21, they can only rotate by rolling along this track. Consequently a rotation of the knob in either direction will produce a rotation of the tubular shaft and ofithe movable plates 15 that are attached to the shaft. However, since a complete rotation of the tubular shaft can be caused only by the rolling of the wheels 20 along the entire circumferential length of the inclined track 21, since the small conical driving wheel 24: must turn more than once to eifect a single rotation of the wheels 20, and since each of the wheels 20 must rotate more than once in order to make a complete circuit of the inclined track, the rate of movement of. the tubular shaft and its attached plates is much less than the rate. at which the knob is turned. (Consequently the operator is able to make fine, adjustments of the position of the movable plates of the condenser by turning the knob through inuch greater angles. In other words, he may obtain'a Vernier adjustment without the manipulation of any other device than the single knob or handle. In the arrangement shown, the ratio of speed reduction .is more than eight to one but any desired ratio may be obtained by properly proportioning the-diameters of the driving and driven wheels and of the annular track. The hub 17 on the disc 1 may be employed for the purpose of attaching the device to a panel. As shown in Fig. 1, the hub is externally screw-threaded at its outer end and is passed through a suitable panel 30 ;,the panel being clamped l between a spacing sleeve 31 surrounding the hub between the panel and the disc and a nut 32 screwed on the outer end of thehub.

a simple and novel variable condenser having built into the same and forming a part thereof a simple planetary gear mechanism adaptneeasio ed greatly-to reduce the rate of movement transmitted by a driving member to a driven member; or in other words, a greatly decreased angle of movement of themovable plates of the condenser for any given annular movement of the actuating knob or handle. a

While I have illustrated and described with particularity only a single preferred form of my invention, I do not desire to be limited to the exact structural details thus illustrated and described; but intend to cover all forms and arrangement which come within the definitions of my invention consti tutingthe appended claims. K

I claim: l

1. In combination, a supporting frame having a wall provided with an annular track in the form of a short frustum of a cone, a tubular shaft co-axial with said track, a resilient .device yieldable in the direction of the axis of the shaft fixed to the latter in the vicinity of said wall, a group of wheels mounted on said device so as to be capable of rotating about axis parallel with the axis of the shaft, the wheels being so disposed that allof them, are in rolling contact wit-h said track, an actuating shaft extending through the tubular shaft, a frustoconical wheel on said actuating shaft in the space between and in engagement with the aforesaid wheels, the larger end of the Wheel on the actuating shaft being directed toward said wall, and means for exerting a pressure on said actuating wheel in a direction tendingto force it away from. said walL,

2. In combination, a frame having a wall provided on the inner side with an annular track in the form ofa shortifrustum of a cone, a movable device supported within said frame so asto be rotatable about of said track, a spider of spring material fixed to said device and lying adjacent to and parallel with said wall, a group of wheels mounted on said spider at equal distances from said axis and each rotatable about its individual axis, the aforesaid wheels being in the form of frustums of cones each making a line cgntact with said track, an actuating wheel in the form of a frustum of a cone disposed oppositely to the other wheels in the'space between,and' in contact with the latter, means-for rotating the actuating wheel, and an adjustable stop engaged with that face of, the actuating wheel directed toward said wall to hold X this wheel in contact with the other wheels; Itwill thus'be seen that I have produced nanoiin iasrro'rwarn the axis 

